The disclosure of Japanese Patent Application No. 2000-258971 filed on Aug. 29, 2000, including the specification, drawings and abstract is incorporated herein by reference in its entirety.
1. Field of Invention
The invention relates to an alarm device that generates an alarm when the distance between a vehicle and an object in front of the vehicle becomes smaller than a set distance.
2. Description of Related Art
An alarm device as disclosed in Japanese Laid-open Patent Publication No. 8-192659 is adapted to generate an alarm when the inter-vehicle distance between a vehicle and a preceding vehicle becomes equal to or smaller than a set distance that is determined based on a relative velocity between the vehicle and the preceding vehicle.
However, the alarm device as disclosed in the above-identified publication may generate an alarm in different timing from that expected by the driver or vehicle operator, and the driver may feel uncomfortable or embarrassed. For example, when the vehicle is in the course of decelerating, the driver may feel that the timing of generation of an alarm is too early.
It is therefore an object of the invention to provide an alarm device that generates an alarm based on a distance between the vehicle and an object that exists in a set region in front of the vehicle, so that the driver or vehicle operator feels less confused or uncomfortable.
To accomplish the above and/or other objects, one aspect of the invention provides an alarm device that generates an alarm when a distance between a vehicle and an object that exists in a set region in front of the vehicle is smaller than a set distance, which alarm device comprises a controller that: (1) determines a tentative set distance based on at least one of a running speed of the vehicle and a relative velocity between the vehicle and the object; and (2) corrects the determined tentative set distance, based on at least a deceleration of the vehicle, so as to determine a final set distance.
The alarm device as described above is adapted to generate an alarm when the distance between the vehicle and the object becomes equal to or smaller than the final set distance determined by the controller. The final set distance is obtained by correcting the tentative set distance determined based on at least one of the relative velocity and the running speed of the vehicle, based on the deceleration of the vehicle. For example, the tentative set distance is corrected so that the final set distance is set to a smaller value as the deceleration becomes larger. Thus, an alarm is less likely to be generated when the deceleration is relatively large, as compared with when the deceleration is relatively small.
Generally, the driver has a sense of safety or security in the case where the vehicle is in the course of decelerating. If the set distance determined in this case is the same as that determined while the vehicle is not decelerating, the driver may feel that the alarm is not very useful or redundant, or that the timing of generation of the alarm is too early. In view of this situation, if it makes it more difficult (less likely) to generate an alarm by setting the set distance to a smaller value, the driver is less likely to feel confused or uncomfortable.
In general, the deceleration of the vehicle increases when the vehicle is running on an uphill, and decreases when the vehicle is running on a downhill. Since the final set distance is made longer with a reduction in the deceleration of the vehicle according to the invention, an alarm is advantageously generated relatively early when the vehicle is running on a downhill.
The set region as indicated above is determined, for example, based on a region in which an object can be detected by an object detector. While the object detector functions to detect an object in a set region in front of the vehicle, the set region may be a region that extends in a two-dimensional field, or a region that extends in a three-dimensional field. One type of the object detector, such as a laser radar device, may be arranged to detect an object based on the receiving state of an electromagnetic wave that is emitted forward of the vehicle and is reflected by the object. Another type of the object detector, such as that including a CCD camera, may be arranged to detect an object based on image information captured by the detector. In the former type of the detector, the set region may be determined based on a region that is common to a region irradiated with the electromagnetic wave and a region in which the reflected wave can be received. In the latter type of the detector, the set region may be determined based on a region in which an image can be captured by a CCD camera. These regions in which an object can be detected depend on, for example, the function or performance of the object detector, but may also depend on the weather, and other conditions. For example, the set region, when it is a two-dimensional region, may be defined based on at least one of: (a) an irradiation angle of electromagnetic wave in the horizontal direction, and (b) a shorter one of the irradiation distance of the electromagnetic wave and the receiving distance of the reflected wave. The set region, when it is a three-dimensional region, may be defined based on, for example: (c) the irradiation angle of electromagnetic wave in the horizontal direction, (d) the irradiation angle of the wave in the vertical direction, and (e) the shorter one of the irradiation distance and the receiving distance.
The object that exists in the set region is not limited to a moving object. The invention is equally applicable to the case where the object is in a stationary state, as well as the case where the object is in a moving state.
According to one preferred embodiment of the invention, the controller sets a correction value used for correcting the tentative set distance, to a smaller value, as the deceleration of the vehicle increases.
The final value of the set distance may be obtained by, for example, adding the correction value based on the deceleration to the tentative set distance, or by multiplying the tentative set distance by the correction value. The correction value is reduced with an increase in the deceleration of the vehicle. As a result, the final set distance can be made longer as the deceleration increases, so that an alarm is less likely to be generated.
When the final set distance is obtained by adding the correction value to the tentative set distance, the correction value can be reduced by increasing the absolute value of the correction value when it is a negative value, or by reducing the correction value when it is a positive value.
When the final set distance is obtained by multiplying the tentative set distance by the correction value, the correction value is set to 1 when the deceleration is equal to a reference value, and is set to be smaller than 1 when the deceleration is larger than the reference value. Furthermore, the correction value is set to be larger than 1 when the deceleration is smaller than the reference value.
According to another preferred embodiment of the invention, the controller determines the tentative and/or final set distance taking account of a relative positional relationship between the vehicle and the object, which relationship is requested by a vehicle operator.
The alarm device according to the above preferred embodiment of the invention takes the relative positional relationship requested by the driver into consideration when determining the set distance. For example, the set distance is made larger when a desired distance as the relative positional relationship requested by the vehicle operator is larger, as compared with the case where the desired distance is smaller. With this arrangement, the vehicle operator feels less confused or less uncomfortable upon generation of the alarm.
As the relative positional relationship requested by the vehicle operator, a desired relative velocity, a desired relative deceleration, a desired approach time, and so forth, may be considered in addition to or in place of the desired distance. For example, the requested relative positional relationship may be set through an operation or manipulation by the vehicle operator, or the like. The vehicle operator sets the desired inter-vehicle distance, inter-vehicle time, and the like, by manipulating an operating member, such as a switch, or a touch panel.
According to a second aspect of the invention, there is provided an alarm device that generates an alarm when a distance between a vehicle and an object that exists in a set region in front of the vehicle is smaller than a set distance, comprising a controller that: determines a tentative set distance based on at least one of a running speed of the vehicle and a relative velocity between the vehicle and the object; and corrects the determined tentative set distance, based on at least a relative deceleration between the vehicle and the object, so as to determine a final set distance.
In the alarm device as described above, the final set distance is obtained by correcting the determined tentative set distance, based on the relative deceleration. The relative deceleration represents the tendency of the vehicle to be separated or spaced apart from the object, which will be called xe2x80x9cseparation tendencyxe2x80x9d, or the tendency of the vehicle to approach the object, which will be called xe2x80x9capproach tendencyxe2x80x9d. The relative deceleration increases with an increase in the separation tendency. If the alarm device generates an alarm in the same timing, the driver is more likely to feel that the timing of generation of the alarm is too early as the separation tendency becomes stronger. If the final set distance is made smaller as the separation tendency becomes stronger, the driver is less likely to feel confused or uncomfortable upon generation of an alarm.
In one embodiment of the above aspect of the invention, the controller determines the final value of the set distance by correcting the tentative set distance based on both a deceleration of the vehicle and the relative deceleration between the vehicle and the object.
In another embodiment of the invention, the controller sets a correction value for correcting the tentative set distance, to a smaller value, as the tendency of the vehicle to be separated from the object is stronger, as compared with the case when the tendency of the vehicle to approach the object is stronger.
The correction value determined based on the relative deceleration is increased as the tendency of the vehicle to approach the object becomes stronger, so that the final value of the set distance is increased. The final set distance may be obtained by adding the correction value to the tentative set distance, or by multiplying the tentative set distance by the correction value.
In another embodiment of the invention, the controller determines at least one of the tentative set distance and the final set distance with reference to a map or maps.
If the map is prepared in advance and stored in, for example, ROM, the set distance can be easily determined using the map.
According to a third aspect of the invention, there is provided an alarm device that generates an alarm when a distance between a vehicle and an object that exists in a set region in front of the vehicle is smaller than a set distance, comprising a controller that: determines the set distance based on (a) at least one of a running speed of the vehicle and a relative velocity between the vehicle and the object, (b) a deceleration of the vehicle, and (c) a relative deceleration between the vehicle and the object.
According to a fourth aspect of the invention, there is provided an alarm device that generates an alarm when a distance between a vehicle and an object that exists in a set region in front of the vehicle is smaller than a set distance, comprising a controller that: determines the set distance based on (a) at least one of a running speed of the vehicle and a relative velocity between the vehicle and the object, and (b) a relative deceleration between the vehicle and the object.
According to a fifth aspect of the invention, there is provided an alarm device that generates an alarm when a relative positional relationship between a vehicle and an object that exists in a set region in front of the vehicle represents a tendency of the vehicle to approach the object as compared with a set relative positional relationship, comprising a controller that: determines a tentative set relative positional relationship based on at least one of a running speed of the vehicle and a relative velocity between the vehicle and the object; and corrects the determined tentative set relative positional relationship, based on at least one of a deceleration of the vehicle and a relative deceleration between the vehicle and the object, so as to determine a final set relative positional relationship.
The alarm device according to the above aspect of the invention may generate an alarm based on a parameter other than the distance between the vehicle and the object. For example, an alarm may be generated when the approach speed as a relative velocity is greater than a set speed, or when the relative deceleration indicates a stronger tendency of the vehicle to approach the object, as compared with a certain criterion. Thus, an alarm may be generated based on the relative velocity or the relative deceleration.
According to a further aspect of the invention, there is provided a running control apparatus, comprising: (1) the alarm device according to any of the above aspects of the invention, and (2) a running controller that controls a running state of the vehicle based on a relative positional relationship between the vehicle and the object.
In one embodiment of the above aspect of the invention, the running controller, during performance of a cruise control, controls the running state of the vehicle so that the vehicle and a preceding vehicle as the object are kept in a relative relationship that is requested by a vehicle operator or driver.
In another embodiment of the above aspect of the invention, the running controller, during performance of a deceleration control, decelerates the vehicle by applying a brake so as to restrain rotation of a wheel of the vehicle.
For example, the deceleration control may apply a brake when the distance between the vehicle and the object becomes equal to or smaller than the final set distance. In this case, an alarm is generated upon application of the brake.